Quasi-periodic behavior of ion events and wave activity upstream from Jupiter's Bow Shock: Ulysses' observations

Abstract

A new insight into the ways that the Jovian magnetosphere influences the near Jupiter interplanetary space becomes possible thanks to Ulysses' collection of magnetic field, plasma and energetic ion (HI-SCALE) data during its inbound trajectory (d22-d34, 1992). The most striking new results from the analysis of those data are the following: a) presence of large amplitude (ΔB_⊥/B≈1) near plane polarized Alfvén waves upstream from the Jovian bow shock with a period equal to the planet’s rotation (∼10h) at times when the Interplanetary Magnetic Field (IMF) was in contact with the bow shock/magnetopause and lay well outside the ecliptic; b) observation of ∼10h quasi-periodic variation in the ion plasma and energetic ion data up to energies of ∼2 MeV, c) existence of a variation with a period 2.5 h ≤T ≤6.5 h in the magnetic field and the ion data, in several cases, d) detection of magnetic waves and charged particle modulation with a period of ∼40min, e) observation of an ∼10 h inward/outward motion of the Jovian magnetopause. The observations are consistent with generation of the low frequency upstream (Alfvén) waves through periodic injection of plasma/energetic ions from within the magnetosphere into the upstream region.